Femtosievert is 1e-15 sievert units.
Femtosieverts to Megasieverts Converter — fSv to MSv
Convert Femtosievert (fSv) to Megasievert (MSv) using the exact conversion factor (1 femtosievert = 1e-21 megasievert). See the formula, worked examples, and conversion table.
Femtosieverts to Megasieverts converter
Converter
Radiation Converter
Convert radioactivity, absorbed dose, and equivalent dose units by compatible radiation family.
Context values
Some unit families need one extra value for a physically accurate result.
Megasievert is 1000000 sievert units.
Result = input x 1e-15 / 1e+6.
Equivalent Dose units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Femtosieverts to Megasieverts
Femtosievert and Megasievert both belong to the radiation-measurement family, though radiation quantities fall into genuinely distinct categories: absorbed dose (gray, rad) measures energy deposited in matter, equivalent dose (sievert, rem) weights that for biological harm, and activity (becquerel, curie) measures how often a radioactive source decays — this page only converts between units of the same kind. Specifically: Femtosievert is 1e-15 sievert units, and megasievert is 1000000 sievert units.
Formula
megasieverts = femtosieverts × 1e-21
This factor comes from each unit's defined relationship to the category's base unit: 1 femtosievert equals 1e-15 base units, and 1 megasievert equals 1000000 base units, so dividing one by the other gives the direct femtosievert-to-megasievert factor of 1e-21.
Simple example
1 fSv × 1e-21 = 1e-21 MSv
1 femtosievert = 1e-21 megasieverts.
Real-world example
10 fSv × 1e-21 = 1e-20 MSv
10 femtosieverts = 1e-20 megasieverts.
Conversion table
| Femtosievert (fSv) | Megasievert (MSv) |
|---|---|
| 0.001 fSv | 1e-24 MSv |
| 0.01 fSv | 1e-23 MSv |
| 0.1 fSv | 1e-22 MSv |
| 1 fSv | 1e-21 MSv |
| 10 fSv | 1e-20 MSv |
| 100 fSv | 1e-19 MSv |
Reverse conversion: Megasievert to Femtosievert
1e-21 MSv × 1e+21 = 1 fSv
1e-21 megasieverts = 1 femtosieverts.
femtosieverts = megasieverts × 1e+21
For a page dedicated to this direction, see Megasievert to Femtosievert.
Understanding the Femtosievert (fSv)
Femtosievert is 1e-15 sievert units.
Understanding the Megasievert (MSv)
Megasievert is 1000000 sievert units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many megasieverts are in 1 femtosievert?
1 femtosievert equals 1e-21 megasieverts, using the exact defined conversion factor rather than an estimate.
How do I convert femtosievert to megasievert?
Multiply the femtosievert value by 1e-21. The converter above does this instantly to whatever precision you set.
How do I convert megasievert back to femtosievert?
Use the reverse factor: 1 megasievert equals 1e+21 femtosieverts. You can also use the swap control in the converter above to flip the direction instantly.
What is a femtosievert?
Femtosievert (fSv) is a unit of radiation.
What is a megasievert?
Megasievert (MSv) is a unit of radiation.
Is the femtosievert to megasievert conversion exact?
Yes. Both femtosievert and megasievert are defined by fixed standards rather than physical artifacts, so the factor of 1e-21 used above is exact to as many digits as you choose to display.
What's the difference between absorbed dose, equivalent dose, and activity?
Absorbed dose (gray, rad) measures the energy radiation deposits in matter. Equivalent dose (sievert, rem) adjusts that figure for how harmful different types of radiation are to biological tissue. Activity (becquerel, curie) measures how often a radioactive source decays, independent of how much dose a person actually receives from it.